This invention relates to particulate oxygen absorbent having good flowability.
In order to preserve foodstuffs, such as vegetables, fish, shellfish, meats, processed foodstuffs, such as potato chips, cakes, peanuts, etc., and so on, it is necessary to prevent the foodstuffs from becoming moldy and from putrefying. Prior art methods have used freezer storage, cold storage, vacuum packaging and replacing the gas present in the inner part of packaging by an inert gas for preventing foodstuffs from becoming moldy and putrefying. Additives, such as anti-oxidant, have been used for preserving foodstuffs. Recently, governments have started to regulate the use of additives for food, since it has been realized that some additives are injurious to humans. The freezer storage method requires large-scale apparatus and complicated operation, so the freezer storage method is costly.
Molds or eumycetes, bacteria and higher organisms such as insects tend to disturb preservation of foodstuffs. These mold, eumycetes, bacteria and insects live and grow in the presence of oxygen and cause putrefaction and change in quality of foodstuffs.
Therefore, if oxygen can be selectively removed from the atmosphere in which the foodstuffs are packed, the problem of putrefaction and change in quality of foodstuff can be overcome, and it will become possible to preserve foodstuffs for a long time.
The prior oxygen absorbents include ascorbic acid type oxygen absorbents and iron type oxygen absorbents. The prior ascorbic acid type oxygen absorbents comprise ascorbic acid or an ascorbate an alkali carbonate or an alkali hydroxide, an iron compound, water and a filler such as activated carbon.
However, prior ascorbic acid type oxygen absorbents have poor flowability, so they have the following disadvantages for a practical use. In general, oxygen absorbents are packed in a permeable bag. The permeable bag containing an oxygen absorbent is packed in an impermeable bag with the foodstuff. In general, oxygen absorbents are normally in particulate or granular form. A die roll type or perseal automatic packaging machine is used for packing such oxygen absorbent in a permeable bag.
However, if the oxygen absorbent in powder form has poor flowability, exact metering is difficult in automatic packaging, and in addition, part of the oxygen absorbent composition adheres to the sealed portion of a packing material, which is not only uneconomical but also gives an unseemly appearance to the final product. Attempt has been made to granulate oxygen absorbent in order to overcome such shortcomings. However, since the prior oxygen absorbent contains filler, such as activated carbon, it is necessary to use a large amount of a binder in order to granulate it. A large amount of a binder contained in the absorbent lowers the oxygen-absorbing property.